This invention relates to an abrasive-blasting method and apparatus for treating a surface. More particularly this invention relates to a closed-environment wet-abrasive blasting system for ejecting abrasive particulate in a water stream through a nozzle area onto a surface to remove surface debris. The water, abrasive particulate and surface debris are vacuumed at the nozzle area, then filtered. Filtered water is recycled through the system.
Abrasive blasting systems eject an abrasive blast stream onto a surface for deburring, abrading, smoothing or removing surface material. Abrasive particulate such as sand, sodium bicarbonate, walnut shells, plastic or other matter are ejected under pressure to impact the surface. The force of impact abrades or cleans the surface removing, coating, contaminants, corrosion or the like (i.e., surface debris). In many applications the abrasive particulate and surface debris are dispersed into the surrounding environment creating a hazardous breathing and work environment. The dispersal of dust into the air is particularly undesirable in indoor or "closed" environments. Plastics and walnut shells for example are used in such applications because less dust is created. It also is known to use a vacuum device to capture the abrasive particulate and surface debris at the nozzle area so that the matter does not escape into the surrounding environment. U.S. Pat. No. 5,319,893 (Hockett) discloses a "Recovery System." U.S. Pat. No. 4,333,277 (Tasedan) discloses a "Combination Sand-Blasting and Vacuum Apparatus".
Wet blasting systems eject the abrasive particulate in a stream of water under pressure. The water stream keeps the dust down, and thus, keeps the ambient air cleaner. U.S. Pat. No. 5,123,206 (Woodson) discloses a "Wet Abrasive Method." Wet blasting systems, however, conventionally release water into the surrounding environment making indoor wet blasting undesirable. Accordingly, there is a need for a wet blasting system which contains the abrasive stream from contaminating the surrounding environment. U.S. Pat. No. 5,049,260 (Spears) disclose a hopper in the blast area into which a waste stream falls. A separation system recycles a wet slurry of blast media. A shortcoming of the hopper is that it is open to the environment and relies on gravity to collect the waste stream. Thus, it is undesirable for indoor use and less applicable for horizontal surfaces.
In addition to avoiding pollution and improving the workplace environment, it also is desirable to recover waste material for re-use. It is known to recover abrasive material from the captured waste stream. U.S. Pat. No. 4,984,397 (Van Leeuwen) discloses an abrasive (dry) blasting system for separating grit and dust through progressive baffling which feeds the grit back into a supply tank for re-use. Spears above includes baffles for separating out large particles, so that small particles and waste water are recycled in a slurry blast system. In many applications, however, it is desirable to substantially filter out the solid particulate from the waste water. Accordingly, there is a need for a closed-environment wet blasting system which recovers and filters the waste water.